Process for making a polymer for an optical substrate by hydrogenating a cycloolefin copolymer

ABSTRACT

Substantially optically clear molding compositions comprising polymerized cycloolefin monomers (e.g., norbornene-type polymers) which, subsequent to polymerization have been hydrogenated are provided. The polymers have a weight average molecular weight of from about 37-47×10 3 .

This is a division of application Ser. No. 07/331,310, filed Mar. 31,1989.

BACKGROUND OF THE INVENTION

This invention relates to optical elements, such as optical recordingmedia, e.g., optical discs, to methods for producing such discs and tomolding compositions for producing them. Articles such as optical discshave generally been made from materials such as polycarbonates orpolymethylmethacrylates. In recent times attempts have been made toproduce such articles from ring-opened polymers. In order to obtainreasonable optical clarity, it was necessary to hydrogenate suchpolymers subsequent to polymerization. However, such polymers have notproved entirely suitable for use in optical applications. For example,molded products of such polymers do not exhibit an optimal spectrum ofproperties, such as good birefringence, melt-flow properties, andrelated properties which may render them not as suitable for use inoptical applications as are already accepted polymers, e.g., thepolycarbonate polymers discussed above.

Polymers obtained by the ring-opening polymerization of cycloolefins arewell known. For example, U.S. Pat. Nos. 4,136,247; 4,136,248; 4,136,249and 4,178,424, all assigned to the B.F. Goodrich Company, describe suchpolymers and their preparation and each is incorporated herein byreference.

The ring-opening polymerization of cycloolefins produces unsaturatedpolycycloolefins. Polycycloolefins obtained from polycycloolefinmonomers, i.e., monomers containing more than one ring structure, e.g.,dicyclopentadiene, are of particular interest. Monomers such asdicyclopentadiene provide a 1,3-cyclopentene repeat structure in thepolymer, which is obtained by a ring-opening polymerization and cannotbe obtained by addition polymerization. These unsaturated polymers areknown to be reactive (sulphur vulcanizable) and they are known toexhibit a profile of properties suitable for, e.g., automotive parts,such as decorative trim.

It is known that saturated hydrocarbon polymers, e.g., polypropylene andpolyethylene, exhibit improved dielectric properties, hydrolyticstability, oxidative stability, and reduced water absorption whencompared to polymers containing ester, amide, alcohol and otherfunctional groups. The dielectric properties of such saturated polymersare desirable for electrical applications when used as insulators. Thehigh oxidative stability of saturated hydrocarbon polymers renders themparticularly desirable for applications in harsh environments, as doestheir hydrolytic stability. When unsaturated polymers are saturated,i.e., when saturated polymers are prepared from unsaturated polymers,the saturated polymers exhibit a dramatic improvement in oxidativestability. However, often that improvement is attained at the expense ofa significant reduction in the heat distortion temperature for thesaturated derivatives of the unsaturated hydrocarbon polymers. Thisreduction in heat distortion temperature may often render the polymersthermally inadequate for end-use in electrical and electro-opticalsystems, despite an improvement in oxidative stability.

Generally, saturated derivatives of ring-opened polymerized cycloolefinsexhibit lower glass transition temperatures, and thus lower heatdistortion temperatures than their unsaturated precursors. Hydrogenatedpolymers of certain cycloolefins have been employed, either in blends,or in particular applications as homopolymers or copolymers. Forexample, Japanese Kokai Patent No. 60 [1985]-26024 discloseshydrogenated "cracked" homopolymers of tetracyclododecene and itscopolymers with bicyclic norbornene. These polymers are disclosed asbeing useful for optical materials having good transparency,water-proofness (low water absorption), and heat resistance, whichrenders them suitable for compact discs, video discs, computer discs,etc.. However, if the teachings of this document are employed to producepolymers disclosed therein, a product exhibiting an inferior spectrum ofproperties results. For example, high glass transition temperaturesneeded for certain applications cannot be obtained with these copolymerswithout sacrificing other properties. Moreover, in addition to the factthat tetracyclododecene is a relatively expensive monomer to make, thematerials of this patent do not exhibit optimized properties.

Japanese Kokoku Patent No. Sho. 58 [1983]-43412 discloses hydrogenatedhomopolymers of dicyclopentadiene wherein the dicyclopentadiene is first"cracked" and polymerized, followed by hydrogenation. The resultantpolymers are disclosed as having improved solvent resistance. Methodsfor hydrogenating the dicyclopentadiene polymers are provided andmethods for polymerization are shown in the examples.

Thus, although attempts have been made to prepare optical materials withsaturated polynorbornene-type polymers, the art still lacks suchmaterials which exhibit an optimum spectrum of properties. There hasbeen a continuing need for improvement.

U.S. Pat. No. 3,557,072 discloses nonhydrogenated polynorbornenes ofgeneral interest which may be of use in applications wherein atransparent polymer is desired.

SUMMARY OF THE INVENTION

It is an object of this invention to provide substrates for opticaldiscs having an improved spectrum of properties, for example, improvedbirefringence, melt-flow indices, dilute solution viscosities, molecularweights, etc., as well as improved optical properties and stability toconditions encountered in the environments in which they will be used.

These and other objects have been attained by providing substantiallyclear molding compositions comprising hydrogenated polynorbornenesderived from at least one norbornene or norbornene derivative or mixturethereof and having a molecular weight of from about 35-5×10³, preferablyabout 37-47×10³. As used herein, molecular weight refers to weightaverage molecular. weight. The polynorbornenes have a moistureabsorption of from about 0.01-0.1 %, preferably about 0.02-0.05%, aretardation (birefringence) of from about 10-80 nm, preferably about10-30 nm, a glass transition temperature (Tg) of from about 110°-160°C., preferably 20-65, preferably about 35-55 and most preferably about47 to about 51, an M-scale hardness of from about 80-130, preferablyabout 100-110, and improved polymer/metal adhesion.

In some preferred embodiments, this invention provides terpolymersderived from monomer mixtures comprising methyltetracyclododecene,methylnorbornene and dicyclopentadiene.

In a process aspect, this invention provides processes for forming asubstantially optically clear molding composition comprisingpolymerizing a monomer of a norbornene or norbornene derivative, or amixture thereof, in the presence of a catalyst effective to promotering-opening polymerization to produce a ring-opened polynorbornene. Theresultant polymer is then hydrogenated to form a substantially opticallyclear polymer having a molecular weight of from about 35-50×10³. Inanother aspect, polymers produced by such processes are provided.

The invention also provides optical discs and other optical mediaproduced by such processes, as well as processes for producing suchoptical media.

DETAILED DESCRIPTION OF THE INVENTION

The polynorbornenes of this invention are derived from cycloolefinmonomers. These cycloolefin monomers are characterized by the presenceof at least one norbornene moiety having the general structureidentified below: ##STR1## This structure may be substituted orunsubstituted. Suitable cycloolefin monomers include substituted andunsubstituted norbornenes, dicyclopentadienes,dihydrodicyclopentadienes, trimer of cyclopentadiene,tetracyclododecenes, hexacycloheptadecenes, ethylidenyl norbornenes andvinylnorbornenes. Substituents on the cycloolefin monomers includehydrogen, alkyl, alkenyl, and aryl groups of 1 to 20 carbon atoms andsaturated and unsaturated cyclic groups of 3 to 12 carbon atoms whichcan be formed with one or more, preferably two, ring carbon atoms. In apreferred embodiment, the substituents are selected from hydrogen andalkyl groups of 1 to 2 carbon atoms. Generally speaking, thesubstituents on the cycloolefin monomers can be any which do not poisonor deactivate the polymerization catalyst. Examples of the preferredmonomers referred to herein include

dicyclopentadiene,

methyltetracyclododecene,

2-norbornene,

and other norbornene monomers such as

5-methyl-2-norbornene,

5,6-dimethyl-2-norbornene,

5-ethyl-2-norbornene,

5-ethylidenyl-2-norbornene (or5-ethylidene-norbornene),

5-butyl-2-norbornene,

5-hexyl-2-norbornene,

5-octyl-2-norbornene,

5-phenyl-2-norbornene,

5-dodecyl-2-norbornene,

5-isobutyl-2-norbornene,

5-octadecyl-2-norbornene,

5-isopropyl-2-norbornene,

5-phenyl-2-norbornene,

5-p-toluyl-2-norbornene,

5-α-naphthyl-2-norbornene,

5-cyclohexyl-2-norbornene,

5-isopropenyl-norbornene,

5-vinyl-norbornene,

5,5-dimethyl-2-norbornene,

tricyclopentadiene (or cyclopentadiene trimer),

tetracyclopentadiene (or cyclopentadiene tetramer),

dihydrodicyclopentadiene (or cyclopentenecyclopentadiene co-dimer),

methyl--cyclopentadiene dimer,

ethyl--cyclopentadiene dimer,

tetracyclododecene

9-methyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4, (ormethyl-tetracyclododecene)

9-methyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4, (orethyl-tetracyclododecene)

9-propyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-hexyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-decyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9,10-dimethyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-methyl, 10-ethyl-tetracyclo[6,2,1,1³,6,0²,7 ] dodecene-4,

9-cyclohexyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-chloro-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-bromo-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-fluoro-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9-isobutyl-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4,

9,10-dichloro-tetracyclo[6,2,1,1³,6,0²,7 ]dodecene-4.

Polymers comprising two or more different types of monomeric units areespecially preferred. For example, copolymers ofmethyltetracyclododecane (hereinafter referred to as MTD) andmethylnorbornene (hereinafter referred to as MNB) are especiallysuitable.

Even more preferably, the polymers of this invention comprise three ormore different types of monomeric units, eg., terpolymers. Thesepreferred terpolymers comprise MTD, MNB and dicyclopentadiene(hereinafter referred to as DCPD). For ease in illustration, the MTDcomponent is designated component A, the MNB component is designated Band the DCPD component is designated C. Suitable components A (MTD-typecomponents) are norbornene-type units derived from norbornene-typemonomers having 4-6 rings. Suitable component A-type monomers can beselected from the list above. Suitable component B-type monomers(MNB-type monomers) are derived from substituted and unsubstitutednorbornenes. Examples include alkylnorbornenes, eg., methylnorbornene.Suitable B-type monomers can be selected from the list above. SuitableC-type monomers (DCPD-type monomers) include substituted andunsubstituted dicyclopentadiene. Examples includealkyldicyclopentadiene, eg., methyldicyclopentadiene. The polymers ofthis invention can exist in the endo- or exo- form and a polymerbackbone of this invention can contain both endo- and exo- forms ofmonomeric units.

Preferred copolymer and terpolymer compositions are listed below:

    ______________________________________                                        A               B       C                                                     MTD             MNB     DCPD                                                  ______________________________________                                        50-95%          0-15%   0-50%                                                 50-90%          2-10%   1-40%                                                 85-90%          3-10%   2-10%                                                 ______________________________________                                    

In the above table, all percentages are by Weight.

An especially preferred terpolymer composition comprises 90%methyltetracyclododecene, 7% methylnorbornene and 3% dicyclopentadiene.

Other monomers can form part of the polynorbornenes such asnon-conjugated acyclic olefins, monocyclic olefins and diolefins. Thenon-conjugated acyclic olefins act as chain terminators. Hexene-1 ispreferred while 1-butene, 2-pentene, 4-methyl-2-pentene, and5-ethyl-3-octene are suitable also. They are typically used at a molarratio of 0.001:1 to 0.5:1 acyclic olefin to cycloolefin monomer.

The polynorbornenes used in this invention are obtained by solutionpolymerization. For solution polymerization, the catalyst preferablycomprises molybdenum or tungsten salts and the co-catalyst preferablycomprises dialkylaluminum halides, alkylaluminum dihalides, alkylalkoxyhalides or a mixture of trialkylaluminum with an iodine source.

Examples of useful molybdenum and tungsten salts include the halidessuch as chlorides, bromides, iodides, and fluorides. Specific examplesof such halides include molybdenum pentachloride, molybdenumhexachloride, molybdenum pentabromide, molybdenum hexabromide,molybdenum pentaiodide, molybdenum hexafluoride, tungsten hexachloride,tungsten hexafluoride and the like. Other representative salts includethose of acetylacetonates, sulfates, phosphates, nitrates, and the like.Mixtures of salts can also be used. For optimal polymerization results,the more preferred salts are the molybdenum halides, especiallymolybdenum pentahalides such as MoCl₅.

Specific examples of co-catalysts for ring-opening solutionpolymerization include alkyl-aluminum halides such as ethylaluminumsesquichloride, diethylaluminum chloride, diethylaluminum iodide,ethylaluminum diiodide, propylaluminum diiodide and ethylpropylaluminumiodide and a mixture of triethylaluminum and elemental iodine.

For solution polymerization, the molybdenum or tungsten salt isgenerally employed at a level of from about 0.01 to about 50 millimolesper mole of total monomer, preferably from about 0.5 to about 10millimoles per mole of total monomer and the organoaluminum compoundsdescribed above are generally used in a molar ratio of organoaluminumcompound to molybdenum and/or tungsten salt(s) of from about 10/1 toabout 1/3, preferably from about 5/1 to about 3/1. Both catalyst andco-catalyst for solution polymerization are normally added after theheating and at the time of polymerization.

Suitable solvents used for the solution polymerization include aliphaticand cycloaliphatic hydrocarbon solvents containing 4 to 10 carbon atomssuch as cyclohexane, cyclooctane and the like; aromatic hydrocarbonsolvents containing 6 to 14 carbon atoms which are liquid or easilyliquified such as benzene, toluene, xylene and the like; and substitutedhydrocarbons wherein the substituents are inert such as dichloromethane,chloroform, chlorobenzene, dichlorobenzene and the like.

Optionally present within the solution are curing agents which initiateradical crosslinking such as the peroxides, di-t-butyl peroxide, or2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3. Antioxidants such ashindered phenol antioxidants, Irganox 1010 and polyunsaturated monomericor oligomeric crosslinkers such as trimethylol propane triacrylate arealso optional.

The polynorbornenes prepared as above are subsequently hydrogenated. Thehydrogenation is fully conventional and well-known to those of ordinaryskill in the art.

Hydrogenation of the ring-opened polymers may be accomplished within thering-opening polymerization solution without isolating the unsaturatedintermediate ring-opened polymers. Alternatively, the polymers may beisolated from the polymerization solution by conventional proceduressuch as coagulation with a non-solvent followed by filtration.Hydrogenation may proceed within solvents such as benzene, toluene,cyclohexane, chlorobenzene or mixtures of such solvents. Thehydrogenated polymers can be isolated from these solvents byconventional isolation procedures such as coagulation followed byfiltration. The isolated polymers can be dried and processed, asdesired, into molded articles.

Hydrogenation of the ring-opened polymerized polymers may beaccomplished by any conventional method used for olefin hydrogenation.The use of transition metal catalysts for olefin hydrogenation iswell-known in the art as indicated by Kirk-Othmer in Encyclopedia ofChemical Technology, 6, (1978), pp. 583-584. James discusses a series oftransition metal catalysts in Advancements in Organometallic Chemistry,17 (1979) 319. In addition, Kirk-Othmer describes transition metalcatalysts suitable for hydrogenation in the Encyclopedia of ChemicalTechnology (1978) at volume 6, page 793 and volume 4, page 842, whichinclude nickel, cobalt, platinum, palladium, chromium, zinc, rhodium andmolybdenum. The portions of the Encyclopedia of Chemical Technologyreferred to above are incorporated herein by reference for theirdiscussion of hydrogenation catalysts and hydrogenation procedures.Complexes of these transition metals are utilized to provide catalystsfor a hydrogenation reaction within a homogeneous system.

The preferred hydrogenation catalysts for these polymers are nickelcomplexes used in conjunction with alkylaluminum co-catalysts.Alternatively, nickel, platinum or platinum on a support such as carbon,calcium carbonate or silica are also excellent hydrogenation catalystsfor these polymers, as is lithium aluminumhydride or diimides. Hydrogenis passed through the catalyst solution to obtain reduction of thepolymers and saturation of the olefinic carbons. It is preferable tomaintain the solution under an inert atmosphere, such as nitrogen orargon to prevent the loss of catalyst activity. Hydrogenation mayproceed at preferred temperatures of from 100°-200° C.

Hydrogenation of the olefinic groups may be substantially complete oronly a portion of these groups may be hydrogenated. Preferably, at least50% of the olefinic groups are saturated by hydrogenation. Hydrogenationimparts greater oxidative stability to the polymers. The hydrogenatedproducts have improved electrical properties and exhibit high heatdistortion temperatures, although the glass transition temperature isbelow those of the unsaturated ring-opened precursors. The reduction inglass transition temperature is acceptable for many opticalapplications.

The polymers of this invention exhibit superior properties with respectto those of importance for materials employed in, for example,environments to which optical discs are subjected. Thus, the polymers ofthis invention exhibit an improved spectrum of properties includingthermal stability, moisture absorption, retardation (birefringence),glass transition temperature, melt-flow properties, stressopticalproperties, density, improved polymer/metal adhesion and greaterhardness. An example of how polymers of this invention compare topolycarbonates conventionally employed in optical discs is set forth inTable I below.

                  TABLE I                                                         ______________________________________                                        Comparison of PNB versus Polycarbonate                                                      PNB        PC                                                   ______________________________________                                        Moisture Absorption                                                                           0.03%        0.2%                                             Retardation     20 nm        60 nm                                            (birefringence)                                                               Tg              133° C.                                                                             138° C.                                   Density, g/ml   1.03         1.3                                              Melt Flow 1200 g/300° C.                                                               50, g/10 min.                                                                              64 g/10 min.                                     Polymer/Metal Adhesion                                                                        Better                                                        Hardness (M Scale)                                                                            110          45                                               ______________________________________                                    

In particular, the polymers of this invention exhibit improved melt-flowcharacteristics. This is significant, because the melt-flow propertiesof a polymer, and therefore the resultant polymeric molding composition,have an important impact on the optical properties of the resultantmolded articles. It is believed that the improved melt-flow propertiesof the polymers of this invention allow the polymer to flow into themold during a molding operation with less stress and that the resultantpolymer therefore exhibits improved birefringence.

It is believed that, at least in part, the improved melt-flow propertiesof this invention are related to the molecular weights exhibited by thepolymers of this invention. The polymers of this invention havingmolecular weights of, e.g., about 35×10³ to about 58×10³ exhibitmarkedly improved melt-flow properties in comparison with the polymersoutside of this molecular weight range. Polymers inside the rangeexhibit melt-flow properties wherein the melt-flow index of the polymersis at least about 40 g per 10 minutes at 1200 g/300° C.

There is a similar relationship between dilute solution viscosity (DSV)and melt flow. When dilute solution viscosities of the polymers arelower than about 0.45, high melt-flow properties are attained, e.g.,melt-flow indexes of at least about 40.

The dilute solution viscosity is determined on a viscometer by standardprocedures. The polynorbornene polymer is weighed out on an analyticalbalance and dissolved in 50 ml of cyclohexane. An amount of from 0.049to 0.051 milligrams of polymer is employed. This solution is thentransferred to a four ounce screw-cap bottle. The bottle is then placedon a shaker for, 10 hours (overnight). Subsequently, the polymersolution is filtered through a B or C grade fritted glass funnel.Twenty-five grams of the filtered solution are pipetted into apreviously weighed aluminum pan. The aluminum pan is placed on a steamplate and the polymer solution is evaporated to dryness. The aluminumpan is cooled and reweighed with the remains of the evaporated solutionto determine the true concentration of the solution. Five milliliters ofthe filtered polymer solution prepared above is then pipetted into anOstwald capilary-type viscometer. This viscometer is thoroughlyconventional and those of ordinary skill in the art can readily employsuch viscometers to determine dilute solution viscosities. Theviscometer is placed in a constant-temperature bath at, e.g., 25°C.±0.1° C. The flow time of the solution is determined to the closest0.1 second. The flow time of the pure solvent is also determined. Thedilute solution viscosity is then calculated according to the followingformula. ##EQU1## where: Ts=time of flow of solution

To=time of flow of solvent

C=concentration of solution

The melt flow index values or melt flow rate is measured on a TiniusOlsen Thermodyne apparatus. In this system, a polynorbornene sample isextruded through a die by a weighted piston. The piston, is 0.376 inchesin diameter. The die is 0.315 inches long and 0.376 inches in diameterhaving a center hole of 0.0825 inches in diameter. In use, the apparatusis preheated to 300° C. and upon equilibrium, 10 grams of polymer ischarged to the barrel. The polymer is preheated for five minutes. Afterthe polymer is preheated, a total of 1,200 grams of pressure, includingthe weight of the piston, is applied to the sample. Samples of theextrudate are collected for every ten seconds until the entire 10 gramsof polymer is exhausted. The samples are weighed on an analyticalbalance. The weights are recorded and multiplied by 60 for melt flowrate, grams for 10 minutes.

To measure birefringence (retardation), sample disks are cast from thepolymer. Birefringence of the sample disk is measured by the use of aCarl Zeiss refractometer with white light, since the difference inretardation between 550 and 630 nanometers (nm) is low (less than 2%).The calculation of retardation is made from a conventionally availabletable of values at a wavelength of 546.1 nm. The difference inretardation between 550 and 546.1 nm would be nominal. The value ismeasured with the sample disk at the 45 degree position in order to findthe characteristic retardation. A typical double pass method measures anaverage retardation from an unoriented sample, giving rise to lowervalues. Since a single pass method is employed, the retardation value isdoubled. The retardation value is reported in nm. Birefringence iscalculated as retardation divided by thickness, where the thickness ismeasured in nm.

The glass transition temperature is determined with a calorimeter.Preferably a Dupont 910 Differential Scanning Calorimeter is employed.From ten to twelve milligrams of the polymer is placed into an aluminumpan and crimped. The crimped sample is placed on the raised platform ofthe heating module. The heating module is purged by pressurized nitrogenfor a specified time before the test is begun. The starting temperatureis about 40° C. with a heating rate of 20° C. per minute. The results ofheat flow versus temperature are recorded and the temperature at thepeak of the curve is recorded as the glass transition temperature.

The water absorption properties of the polymers of this invention aredetermined by ASTM D-570; the Rockwell hardness is determined by ASTMD-785 and the density is determined by ASTM D-792. These standards arehereby incorporated by reference herein.

EXAMPLE 1 Preparation of Hydrogenated Methyl-tetracyclododecene(MTD)/Dicyclopentadiene (DCPD) 90/10 Copolymer

The following pilot plant procedure was used to prepare a hydrogenatedMTD/DCPD copolymer. A feedblend consisting of 4.7 lbs. of DCPD (99%purity), 42.3 lbs. of MTD (98.5% purity), 66.9 lbs. of hexene-1 and193.1 lbs. of cyclohexane was prepared and charged through a 3Amolecular sieve column into a conditioned 50-gallon polymerizationreactor. Then 0.23 lbs. of a 25% ethylaluminum sesquichloride in toluenesolution and 1.55 lbs. of molybdenum pentachloride solution containing1.6% MoCl₅ dissolved in a 75/25 toluene/ethylacetate solution wascharged to the reactor. An exothermic ring-opening polymerizationoccurred immediately and the reaction temperature increased from 80° F.to about 135° F. The reaction was allowed to proceed for 30 minutes andthe polymer solution was transferred to a 50-gallon hydrogenationreactor which contained 2.2 lbs. of a Harshaw Ni 5132 P hydrogenationcatalyst (65% Ni on silica-alumina support) and 4.5 lbs. of Celite500/503 filter aid. The reactor was pressurized with 50 psig of hydrogenand heated to 100° C. The reactor temperature was controlled between100° C. and 130° C. After about two hours, the hydrogen pressure wasincreased to 300 psig for another hour. The polymer solution was thenfiltered (0.4 micron) to remove the hydrogenation catalyst and filteraid. Mark 2112 antioxidant (0.1 part/100 polymer) was added to thepolymer solution. Infrared analysis showed the polymer contained lessthan 0.1% trans-unsaturation.

The polymer solution was extracted with 30 parts of a isopropanol/water88/12 w/w solution and the polymer was isolated by steam stripping. Thefine polymer crumb was dried for 36 hours in a 80° C. vacuum tray drier.

Four runs were made using the procedure shown above and the polymercrumb blended together gave a 141 lb. lot of polymer which was processedthrough a devolatilization twin-screw extruder at zone temperatures of150° C.-300° C. to yield 130 lb. lot of polymer in the form of cleanclear, colorless pellets. The polymer had the following physicalproperties: DSV=0.43, Tg=151° C., 0.0% residual weight loss at 450° C.and a melt-flow of 23 gms/min.

EXAMPLE II Hydrogenated Methyl-tetracyclododecene (MTD)/Methylnorbornene (MNB) 90/10 Copolymer

The following pilot plant procedure was used to prepare a hydrogenatedMTD/DCPD copolymer. A feedblend consisting of 4.6 lbs. of MNB (99%purity), 42.1 lbs. of MTD (98.5% purity), 74.7 lbs. of hexene-1 and183.6 lbs. of cyclohexane was prepared and charged through a 3Amolecular sieve column into a conditioned 50-gallon polymerizationreactor. Then 0.23 lbs. of a 25% ethylaluminum sesquichloride in toluenesolution and 1.59 lbs. of molybdenum pentachloride solution containing1.6% MoCl₅ dissolved in a 75/25 toluene/ethylacetate solution wascharged to the reactor. An exothermic ring-opening polymerizationoccurred immediately and the reaction temperature increased from 80° F.to about 135° F. The reaction was allowed to proceed for 30 minutes.Irganox 1010 antioxidant at a level of 1 part/100 polymer was added tothe reactor. The polymer solution was transferred to a 50-gallonhydrogenation reactor which contained 2.1 lbs of a Harshaw Ni 5132 Phydrogenation catalyst (65% Ni on silica-alumina support) and 4.5 lbs.of Celite 500/503 filter aid. The reactor was pressurized with 50 psigof hydrogen and heated to 100° C. The reactor temperature was controlledbetween 100° C. and 130° C. After about two hours the hydrogen pressurewas increased to 300 psig for another hour. The polymer solution wasthen filtered (1.0 micron) to remove the hydrogenation catalyst andfilter aid. An additional 1 phr Irganox 1010 antioxidant was added tothe polymer solution. Infrared analysis showed the polymer containedless than 0.1% trans-unsaturation.

Six runs were made using the procedure shown above and the polymersolutions blended together in a 300- gallon tank. The polymer solutionwas extracted with 30 parts of a isopropanol/water 88/12 w/w solutionand the polymer isolated by steam stripping. The fine polymer crumb wasdried for 36 hours in a 80° C. vacuum tray drier.

The polymer crumb blended together gave a 243 lb. lot of material. Thismaterial was processed through a devolatilization twin-screw extruder atzone temperatures of 150° C.-300° C. to yield a 233 lb. lot of polymerin the form of clean, clear, colorless pellets. The polymer had thefollowing physical properties: DSV=0.38, Tg=133° C., 0.2% residualweight loss at 450° C. and a melt flow of 50 gms/min.

EXAMPLE III Degradation Results of Saturated and Unsaturated Polymers

Hydrogenated and non-hydrogenated polynorbornenes were prepared. Some ofthe polynorbornene was hydrogenated to provide a saturated sample. A12.73 mg sample of hydrogenated polymer was provided and a 10.5 mgsample of non-hydrogenated (unsaturated) polymer was provided. Thesamples were subjected to various temperatures for equal times and theweight loss, (in percent) was calculated. The temperatures and resultsare set forth below.

    ______________________________________                                                   Saturated                                                                             Unsaturated                                                           Wt. % Loss                                                                            Wt. % Loss                                                            H672A   672A                                                       ______________________________________                                        100° C.                                                                             0.11%     0.18%                                                  200° C.                                                                             2.26%     1.35%                                                  300° C.                                                                             2.50%     3.46%                                                  350° C.                                                                             2.70%     5.39%                                                  400° C.                                                                             3.08%     9.97%                                                  450° C.                                                                             10.11%    67.23%                                                 ______________________________________                                    

The results indicate that the saturated polymer exhibited significantlylower weight loss at elevated temperatures.

EXAMPLE IV Molding of Polymer Into Discs

The saturated and unsaturated polymers of Example III were molded intodiscs having a diameter of about 2". The polymers were heated to atemperature of about 475° F. for about 5 minutes, cooled for 5 minutesand cold-pressed (71° F.) into discs having a diameter of about 2" and athickness of about 0.028" for the non-hydrogenated polymer and about0.012" for the hydrogenated polymer. The discs formed of hydrogenatedpolymer appeared to the unaided eye to be optically clear with thepresence of some bubbles. The discs formed from the non-hydrogenatedpolymer were dark brown, not optically clear, i.e., could not be seenthrough, and appeared to have less structural integrity.

EXAMPLE V

Various blends of polynorbornene of example 1 and the polynorbornene ofexample 2 were prepared. The properties of the blends are listed belowand demonstrate properties which would be expected of copolymers havingthe proportion of monomers indicated.

    __________________________________________________________________________                 Melt Flow   Final Composition                                       PNB of                                                                             PNB of                                                                             300° C./1,200 g                                                                    MTD MNB DCPD                                         Run                                                                              Ex I Ex II                                                                              10 min  Tg, °C.                                                                    %   %   %                                            __________________________________________________________________________    #1 100   0   28      150.6                                                                             90  0   10                                           #2 90   10   35      148.7                                                                             90  1   9                                            #3 75   25   36      145.9                                                                             90  2.5 7.5                                          #4 50   50   40      142.6                                                                             90  5   5                                            #5 25   75   45      137.7                                                                             90  7.5 2.5                                          #6 10   90   49      136.3                                                                             90  9   1                                            #7  0   100  50      134.5                                                                             90  10  0                                            __________________________________________________________________________

EXAMPLE VI

Additional blends of polynorbornenes were prepared from what wasdesignated as PNB-X and PNB-XIV. PNB-X is a polymer comprising 50%monomeric units of MTD and 50% monomeric units of DCPD. PNB-XIV is apolymer comprising 90% monomeric units of MTD and 10% monomeric units ofMNB. Various tests were conducted to determine the following propertiesof the polymeric blends: melt flow, dilute solution viscosity, Tg and,values of various ratios of MTB, MNB and DCPD formulations. As indicatedabove, the behavior of these blends can be correlated to the behavior ofthe actual copolymer or terpolymer comprising repeating units of suchmonomers. The blends, composition of the blends and the measurements ofthe properties discussed above are set forth below.

    __________________________________________________________________________    Sample No.:                                                                           1   2   3   4   5   6   7                                             __________________________________________________________________________    PNB-10  100 80  60  40  20  10  00                                            PNB-14  --  20  40  60  80  90  100                                           Composition                                                                   DCPD    50  40  30  20  10  5   00                                            MTD     50  58  66  74  82  86  90                                            MNB     --  2   4   6   8   9   10                                            Melt Flow*                                                                            55  51  49  48  48  47  48                                            Tg      120.5                                                                             122.5                                                                             125.3                                                                             129.6                                                                             131.5                                                                             134.2                                                                             135                                           D.S.V   0.409                                                                             0.412                                                                             0.411                                                                             0.423                                                                             0.411                                                                             0.419                                                                             0.413                                         Melt Flow**                                                                           104.3                                                                             91.8                                                                              92.1                                                                              92.7                                                                              92.3                                                                              86.9                                                                              91.5                                          % Melt Flow                                                                           90  80  88  93  92  85  91                                            Increase                                                                      M.sub.n 14700                                                                             14300                                                                             14000                                                                             14100                                                                             14200                                                                             13700                                                                             14000                                         M.sub.w 43000                                                                             41700                                                                             41700                                                                             41300                                                                             41700                                                                             40000                                                                             41600                                         M.sub.w /M.sub.n                                                                      2.92                                                                              2.91                                                                              2.96                                                                              2.98                                                                              2.94                                                                              2.99                                                                              2.96                                          __________________________________________________________________________     *gm/10 Min, 1200 gm load @ 300° C.                                     **2162 gm load @ 300° C.                                          

DETERMINATION OF MOLECULAR WEIGHT

The molecular weight (M_(W)) of the polymers was determined by using gelpermeation chromatography (GPC). GPC is a powerful separation technique.The separation takes place in chromotographic columns filled with beadsof a rigid porous "gel." The pores in these gels are of the same size asthe dimensions of polymer molecules.

A sample of a dilute polymer solution in cyclohexane is introduced intoa solvent stream flowing through the column. As the dissolved polymermolecules flow past the porous beads, they can diffuse into the internalpore structure of the gel to an extent depending on their size and thepore-size distribution of the gel. Larger molecules can enter only asmall fraction of the internal portion of the gel, or are completelyexcluded; smaller polymer molecules penetrate a larger fraction of theinterior of the gel. The larger the molecule, the less time it spendsinside the gel and the sooner it flows through the column. The differentmolecular species are eluted from the column in order of their molecularsize as distinguished from their M_(W), the largest emerging first. Aplot of amount of solute versus retention volume can be converted intomolecularsize distribution curves.

The gel permeation chromatography measurements are conducted on achromatograph produced by Waters Associates, specifically a WatersAssociates 150-CALC/GPC. This instrument contains five columns. Thefirst four columns employ a PL gel mixed bed. The final column employs aPL 10 micron substrate. The columns are formed of copper tubing and havea dimension of 300×7.5 mm. The carrier solvent employed is toluene. Thestandard employed is polystyrene.

The sample is prepared by dissolving 0.08 grams of polymer in 3 ml. ofcyclohexene. This mixture is then shaken overnight. The solution is thenmade up to 15 cc using toluene. The instrument is heated to 50° C. andis maintained at the speed of 1 cc/min. The sample is then submitted tothe instrument.

What is claimed is:
 1. A process for forming a substantially clearhydrogenated copolymer suitable for molding into an optical substrate,comprising,a) polymerizing a mixture of comonomers comprising from60-95% methyltetracyclododecene and 5-40% dicyclopentadiene,based on thetotal weight of said mixture, in the presence of a catalyst effective topromote ring-opening polymerization of said comonomers, to yield anunsaturated copolymer; and, b) hydrogenating said unsaturated copolymerto produce said hydrogenated copolymer having a weight average molecularweight in the range from 35×10³ to 50×10³, and a melt flow index in therange from 40-65 g/10 min at 300° C. with a 1.2 kg load, as determinedon a Tinius Olsen melt-flow index system.
 2. A process for forming asubstantially clear hydrogenated copolymer suitable for molding into anoptical substrate, comprising,a) polymerizing a mixture of comonomerscomprising from 85-95% methyltetracyclododecene and 5-15%methylnorbornene, based on the total weight of said mixture, in thepresence of a catalyst effective to promote ring-opening polymerizationof said comonomers, to yield an unsaturated copolymer; and, b)hydrogenating said unsaturated copolymer to produce said hydrogenatedcopolymer having a weight average molecular weight in the range from35×10³ to 50×10³, and a melt flow index in the range from 40-65 g/10 minat 300° C. with a 1.2 kg load, as determined on a Tinius Olsen melt-flowindex system.
 3. A process for forming a substantially clearhydrogenated copolymer suitable for molding into an optical substrate,comprising,a) polymerizing a mixture of comonomers comprising form50-90% methyltetracyclododecene, 2-10% methylnorbornene, and 5-50%dicyclopentadiene, based on the total weight of said mixture, in thepresence of a catalyst effective to promote ring-opening polymerizationof said comonomers, to yield an unsaturated copolymer; and, b)hydrogenating said unsaturated copolymer to produce said hydrogenatedcopolymer having a weight average molecular weight in the range from35×10³ to 50×10³, and a melt flow index in the range from 40-65 g/10 minat 300° C. with a 1.2 kg load, as determined on a Tinius Olsen melt-flowindex system.
 4. A substantially optically clear molding compositionproduced by the process of claim
 1. 5. A substantially optically clearmolding composition produced by the process of claim
 2. 6. Asubstantially optically clear molding composition produced by theprocess of claim
 3. 7. A process for forming a substantially clearhydrogenated copolymer suitable for molding into an optical substrate,comprising,a) polymerizing a mixture of comonomers comprising from60-95% tetracyclododecene and 5-40% dicyclopentadiene, based on thetotal weight of said mixture, in the presence of a catalyst effective topromote ring-opening polymerization of said comonomers, to yield anunsaturated copolymer; and, b) hydrogenating said unsaturated copolymerto produce said hydrogenated copolymer having a weight average molecularweight in the range from 35×10³ to 50×10³, and a melt flow index in therange from 40-65 g/10 min at 300° C. with a 1.2 kg load, as determinedon a Tinius Olsen melt-flow index system.
 8. A process for forming asubstantially clear hydrogenated copolymer suitable for molding into anoptical substrate, comprising,a) polymerizing a mixture of comonomerscomprising from 85-95% tetracyclododecene and 5-15% methylnorbornene,based on the total weight of said mixture, in the presence of a catalysteffective to promote ring-opening polymerization of said comonomers, toyield an unsaturated copolymer; and, b) hydrogenating said unsaturatedcopolymer to produce said hydrogenated copolymer having a weight averagemolecular weight in the range from 35×10³ to 50×10³, and a melt flowindex in the range from 40-65 g/10 min at 300° C. with a 1.2 kg load, asdetermined on a Tinius Olsen melt-flow index system.
 9. A process forforming a substantially clear hydrogenated copolymer suitable formolding into an optical substrate, comprising,a) polymerizing a mixtureof comonomers comprising from 50-90% tetracyclododecene, 2-10%methylnorbornene, and 5-50% dicyclopentadiene, based on the total weightof said mixture, in the presence of a catalyst effective to promotering-opening polymerization of said comonomers, to yield an unsaturatedcopolymer; and, b) hydrogenating said unsaturated copolymer to producesaid hydrogenated copolymer having a weight average molecular weight inthe range from 35×10³ to 50×10³, and a melt flow index in the range from40-65 g/10 min at 300° C. with a 1.2 kg load, as determined on a TiniusOlsen melt-flow index system.
 10. A substantially optically clearmolding composition produced by the process of claim
 7. 11. Asubstantially optically clear molding composition produced by theprocess of claim
 8. 12. A substantially optically clear moldingcomposition produced by the process of claim 9.